With the confirmation of gravitational waves, it got me thinking -- is there an effective elastic modulus for spacetime?
Because the wave propagates, it should be possible I would think to derive a stress-strain relation by determining the amount of length change as a function of force applied.
Has this been done? Is the modulus isotropic or anisotropic (I would guess if it is anisotropic, the anisotropy would be in the time coordinate and the spatial coordinates are isotropic)? Would it be linear or nonlinear?